Fixing WinCC V7.4 raPopupDevice C-Script Failure After Migrating from V7.0 SP1

After migrating a Siemens WinCC V7.0 SP1 project to WinCC V7.4 the migration log reports Completed, but the runtime cannot open faceplates invoked from a C-action with the Graphics API call raPopupDevice(lpszPictureName, TAG). The script compiles without warnings, the picture compiles, and the Web Navigator preview may even resolve the tag — yet the popup faceplate never appears on the local runtime, or it appears but the connected tag references are no longer bound.

This article documents the root cause, the diagnostic procedure with the APDiag tool, the role of OS compilation from SIMATIC Manager, the language/Unicode pitfalls with Russian (Cyrillic) project data, and the field-verified resolution path that brings the faceplate call back online without rolling back the migration.

1. Problem Definition

1.1 Symptom Table

1.2 Reference C-Action

The failing action is typically bound to a button's Mouse > Click event:

#include "apdefap.h"
void OnClick(char* lpszPictureName,
             char* lpszObjectName,
             char* lpszPropertyName)
{
    #define TAG "PLC/Pr_10"
    raPopupDevice(lpszPictureName, TAG);
}

Faceplate is generated with RA (Runtime API / Reference Application) v1.2 Build 14. The same faceplate functioned correctly in V7.0 SP1 prior to migration.

2. Affected Versions and Environment

3. Root Cause Analysis

Three independent failure paths converge on the raPopupDevice call. Each must be ruled in or out before the issue can be declared resolved.

3.1 OS Compilation Re-link of C-Script Image

In PCS 7 / WinCC the Compile OS step performed from SIMATIC Manager regenerates the C-script binary database (*.pwl, *.pck, PDLRT) and re-links internal function pointers. The first RT start after migration executes the pre-compile image and the C-action works. As soon as the engineer runs Compile OS, the new image is loaded and raPopupDevice resolves to a NULL function pointer because the C-export table for faceplate-related APIs (group RA_*) is rebuilt with a different ordinal set in V7.4.

3.2 Project Language and Cyrillic FB/DB Comments

Russian-language FB and DB comments are stored in V7.0 SP1 using the Windows ANSI code page (CP1251). V7.4 stores all comments in Unicode (UTF-16). When Convert Project Data is run with the wrong project language, comments are corrupted, the font is replaced with a Western substitution, and the C-action's Pre-compile step can fail to parse the surrounding picture, leaving the click handler unregistered. Selecting English in the project language dialog causes Russian strings to display as ????? because no fallback font is mapped; selecting Russian preserves the text but the C-script still fails until the OS image is rebuilt correctly.

3.3 Web Navigator vs Local Runtime Hand-off

Web Navigator uses a separate picture cache (WebNav\PicCache) and a dedicated C-script interpreter process (WebNavRT.exe). The local runtime uses CCEServer.exe and PDLRT.dll. The two processes are not synchronised, which is why tag values that look correct in the browser can be missing in the local runtime and vice versa.

4. Diagnostic Procedure with APDiag

The official Siemens support entry 22196555 — "How do you start the APDiag script diagnostics tool?" and the follow-up 22196775 — "How do you use APDiag to debug C scripts?" provide the canonical tool for isolating this class of issue. The procedure is:

1. Start APDiag from the WinCC installation directory: <InstallDir>\WinCC\ApDiag\apdiag.exe, or via the Windows start menu entry Siemens Automation > WinCC > Tools > APDiag.
2. In APDiag enable Capture C output and Log to file. Set the log path to a directory writeable by the runtime service account.
3. Add temporary printf() traces inside the failing C-action:

   #include "apdefap.h"
   void OnClick(char* lpszPictureName,
                char* lpszObjectName,
                char* lpszPropertyName)
   {
       printf("OnClick enter pic=%s obj=%s prop=%s\n",
              lpszPictureName, lpszObjectName, lpszPropertyName);
       #define TAG "PLC/Pr_10"
       int rc = raPopupDevice(lpszPictureName, TAG);
       printf("raPopupDevice returned %d, last err=%d\n",
              rc, GetLastError());
   }

4. Activate the WinCC runtime. Click the button. Observe the APDiag console.
5. Expected healthy output:

   OnClick enter pic=Overview_Master::Overview obj=btn_FaceplatePopup prop=MouseAction
   raPopupDevice returned 0, last err=0

6. Failure signature A (post-OS-compile):
   raPopupDevice returned -1, last err=127 — the C-export ordinal could not be resolved.
7. Failure signature B (language):
   OnClick entry log is missing entirely. The action has not been registered; the picture cache references an absent language DLL.
8. Failure signature C (tag not bound):
   raPopupDevice returned 0, last err=0 but the popup contains the placeholder design. The tag prefix PLC/ cannot be resolved in the new channel unit table.

Capture the log, attach it to the project backup, and proceed to the resolution matrix that matches the observed signature.

5. Step-by-Step Resolution

5.1 Pre-conditions

• Full project backup of the V7.4 directory (typically D:\WinCC_Projects\<ProjectName>\<ComputerName>) before any change.
• Export the entire project to a .zip via WinCC Explorer Project > Archive.
• Confirm no client is currently running (CCEServer.exe and WebNavRT.exe absent in Task Manager).

5.2 Procedure

1. Verify project language. In WinCC Explorer right-click the project root, choose Properties > Project Language. Set the active language to Russian if the source contained Cyrillic FB/DB comments. Close the dialog with OK; this triggers an internal language re-index.
2. Re-run Convert Project Data. From the menu Tools > Convert Project Data select the language that matches the original V7.0 SP1 deployment (in this case Russian). The conversion rebuilds the *.pwl script database with the correct Unicode mapping.
3. Clear picture and script cache. Stop the runtime service. Delete the contents of <ProjectPath>\<ComputerName>\Pictures, ...\Library, ...\WebNav\PicCache and ...\WebNav\Library. Do not delete the GraCS directory; only the compiled *.pdl_ shadow files are removed by WinCC on next RT start.
4. Decide on OS compilation order. Two verified orderings are possible. Pick the one that matches your topology:
   • Order A — Local-first: start runtime immediately after Convert Project Data, confirm faceplate opens, then run Compile OS from SIMATIC Manager. This is the safest order for stand-alone single-station projects.
   • Order B — Server-first: in redundant / multi-client PCS 7 topologies run Compile OS on the engineering station, transfer the OS image to the server, then start the runtime on the server, and only afterwards load Web Navigator clients.
5. Recompile the C-scripts. In WinCC Explorer select Tools > C-Editor > Rebuild All. The dialog should report OK for every script. Any E0001 entry indicates a hard error and must be fixed before continuing.
6. Regenerate the faceplate instances. Open the picture that contains the faceplate invocation. Use Right-click > Faceplate > Update Instance for every instance. This re-binds the C-export reference table.
7. Restart the runtime service and re-test the button with APDiag running.

6. Language Handling for Russian and Mixed-Language Projects

Russian-language WinCC projects are particularly exposed because CP1251 text in V7.0 SP1 must be promoted to UTF-16 in V7.4. The following rules apply:

7. OS Compilation Pitfalls with SIMATIC Manager

The Compile OS step in SIMATIC Manager is mandatory for PCS 7 projects, optional for stand-alone WinCC, and always a risk for C-script projects migrated from V7.0 SP1.

7.1 When to avoid Compile OS

• The WinCC project is stand-alone (no AS / no S7 connection) and the engineering station is the runtime server. Compile OS is unnecessary and can be skipped.
• The project uses RA v1.2 Build 14 or earlier faceplate generators. These build faceplate instance structures in a layout that the V7.4 OS compiler does not fully understand; compilation succeeds but the resulting faceplate instance is silently dropped from the PDL.

7.2 When Compile OS is required

• PCS 7 AS-OS engineering is in use; the AS symbols must be re-exported.
• Redundancy partner configuration is changed.
• S7 connection passwords are re-issued.

7.3 Recommended sequence for PCS 7 with migrated C-scripts

1. Complete the WinCC migration in WinCC Explorer.
2. Run Convert Project Data with the correct language.
3. Open SIMATIC Manager, perform Compile OS with the option Scope: Entire OS.
4. Re-open WinCC Explorer; the OS compile will have flagged a download requirement. Perform the download to the target server.
5. Rebuild the C-scripts (Tools > C-Editor > Rebuild All).
6. Verify the picture cache is regenerated on the server (look for new *.pdl_ shadow files in GraCS).
7. Start the runtime.

8. Verification Matrix

9. Edge Cases and Field Caveats

9.1 raPopupDevice vs. ShowPopup

WinCC V7.4 still supports the older raPopupDevice C-API for backward compatibility, but newly written code should use ShowPopup (VBS) or HMIRuntime.ActiveScreen.ShowPopup (VBS). raPopupDevice is bound to the legacy apdefap.h header; if you have the option to refactor, do so — but only after stabilising the runtime, never during the migration itself.

9.2 Mixed 32/64-bit Runtime

WinCC V7.4 SP1 added experimental 64-bit runtime support. If the engineering station was upgraded to 64-bit but the runtime server remained 32-bit, the C-export ordinal table differs by 1 between the two. The C-script image compiled on the 64-bit station will fail to register on the 32-bit server. Always compile the C-scripts on the same bitness as the runtime host.

9.3 Hotfix Availability

Siemens has released several hotfixes targeting faceplate C-API regressions. Always update to the latest available WinCC V7.4 Update release on both engineering station and runtime server before opening a service request. The hotfix bundle includes PDLRT.dll, CCEServer.exe, and the apdiag.exe update.

9.4 Anti-virus Interference

Real-time AV scanning of GraCS\*.pdl_ files during RT startup can corrupt the picture cache and cause intermittent raPopupDevice failures. Add the project directory and %ProgramFiles%\Siemens\WinCC to the AV exclusion list. This is a particularly common source of intermittent failures that disappear after a reboot.

9.5 When to Escalate to Siemens Support

If the APDiag trace shows raPopupDevice returned -1, last err=126 (module not found), capture the project archive plus the APDiag log and open a service request. The error indicates a missing or corrupted C-export DLL and cannot be fixed in the field without re-installing the WinCC runtime components.

10. Alternative Workarounds

10.1 VBS Replacement for raPopupDevice

If the C-action cannot be stabilised, replace it with a VBS action. The semantic equivalent is:

Sub OnClick(ByVal Item)
    Dim sTag
    sTag = "PLC/Pr_10"
    HMIRuntime.ActiveScreen.ShowPopup "<FaceplateName>", sTag, , , , , , , , , , False
End Sub

This bypasses the apdefap.h C-API entirely. Note that ShowPopup has a different parameter list from raPopupDevice; consult the WinCC V7.4 VBS reference for the exact argument signature.

10.2 Down-Compiling Strategy

If neither resolution path is acceptable, the project can be kept on V7.0 SP1 until the faceplate generator is upgraded. WinCC V7.0 SP1, SP2, SP3 all share the same C-export ordinal table; migration can therefore be deferred without technical risk, although Microsoft mainstream support for Windows Server 2008 R2 ended in January 2015 and security patches are no longer delivered.

10.3 Custom C-Export Wrapper

For projects with a large installed base of raPopupDevice calls, an intermediate wrapper can be compiled that re-exports the V7.4 ordinals under the V7.0 SP1 names. This is a last-resort option and requires a deep understanding of the WinCC C-API and the ability to rebuild the C-script database.

11. Summary of the Verification Flow

The recommended end-to-end verification sequence after the resolution procedure is:

1. Confirm the project language matches the original deployment language.
2. Confirm Convert Project Data has been run with that language selected.
3. Confirm the C-Editor reports zero E0001 errors on a full rebuild.
4. Confirm the OS compile (if performed) reports zero warnings on the C-script section.
5. Confirm the APDiag trace shows raPopupDevice returned 0, last err=0 on a click.
6. Confirm the faceplate instance visually updates with live tag values from PLC/Pr_10.
7. Confirm the same behaviour on a Web Navigator client.

If any of the seven checks fail, return to the section that owns the failing check and re-apply the corresponding remediation. Do not move forward until all seven pass.

12. Frequently Asked Questions